Glaciation during the Late Palaeozoic Ice Age

ISBELL, J. L.; GRIFFIS, N.P; MUNDIL, R; MOXNESS, L.D.; TABOADA, A.C.; MONTAÑEZ, I.P.; VEDERNIKOV, I.L; BIAKOV, A.S; CICCIOLI, P.L.; GULBRANSON, E.L.; FEDORCHUK, N.D.; LIMARINO, C.O.; PAGANI, M.A.

Congreso; 35 th Internatinal Geological Congress; 2016

The late Palaeozoic Ice Age (LPIA) was one of Earth?smost important climatic events as it played an important role in driving linkedoscillations in climate, sea level, and floral and faunal restructuring duringthe Carboniferous and Permian. Despite an evolving understanding, the size,distribution, paleogeography, timing, depositional settings, and possiblebipolarity of the glaciations remain unresolved. Although Gondwana glaciationis well established, traditional views evoke waxing and waning of anAntarctic-centred ice sheet across much of the supercontinent. This model resultsfrom interpreting diamictites, soft sediment grooves, and deformed strata assubglacial and/or ice-contact deposits. Such reasoning is simplistic as suchfeatures are also produced by glaciomarine and non-glacial mass-transportprocesses. More recent LPIA studies suggest that numerous, smaller ice centreswaxed and waned diachronously across Gondwana with glacial intervals on thescale of a few Ma alternating with non-glacial intervals of equal duration.LPIA glaciation likely started in the Late Devonian (Famennian) in northernSouth America and west-central Africa, possibly reoccurred in the Tournaisian,and began in earnest in the Viséan of South America. Widespread glaciationoccurred in southern South America during the late Serpukhovian-Bashkirian.However, not all of South America was covered by ice as evidenced in theeastern Paganzo Basin where strata originally identified as glacigenic wereinstead deposited by alluvial fans and rock falls into lake deposits within a deeply-incised,narrow, non-glacial valley. Following the mid-Carboniferous, glacigenicdeposits disappear from western Argentina and were replaced by increasinglyarid, non-glacial successions. Farther east, new evidence suggest that glacierssurrounding the Paraná Basin continued feedingice into the basin until they finally disappeared near the end of thePennsylvanian. In eastern Australia, at least 4 glacial episodes occurred inthe Carboniferous starting in the Serpukhovian and ending in the Moscovian.Based on current dating and biostratigraphy, widespread glaciation (southernmostSouth America, southern Africa, Antarctica, the Arabian Peninsula, India, andAustralia) occurred again possibly starting in the latest-most Pennsylvanianand extending into the Early Permian (Asselian and Sakmarian). Following thispotential glacial maxima, glacigenic strata are only reported from high mid -latitudebasins in eastern Australia, which contain strata that represent 3 to 4additional glacial/cold intervals. This is in marked contrast to Antarctica,which rested over the South Pole and occupied most of Polar Gondwana. Antarctica?sMiddle to Late Permian strata are characterized by extensive fluvial coalmeasures, fossil forests lacking evidence of frost damage, and a geochemicalsignal suggesting temperate paleoclimatic conditions similar to the U.S.Pacific Northwest.  Reportedglaciation in the Northern Hemisphere is based primarily on the occurrence ofCapitanian diamictites in north-eastern Russia. Recent work indicates that thesestrata were not glacigenic in origin but rather were deposited as volcanicdebris flows and slides/slumps associated with concurrent activity in the Okhotsk-Taigonosvolcanic arc, which was located along the leading edge of Pangea as it driftedacross the North Polar Circle. Therefore, bipolar glaciation cannot beconfirmed.